In the design of electrical resistors, packaged for use in radios, computers, space equipment or electronics gear in general, there is an ongoing common design problem. Irrespective of whether the electrical resistor is from the carbon, carbon-resin, metal film, metal foil or metal oxide varieties, the resistor element should be protected from stresses which can change the value of the resistance or from moisture which can ultimately change the resistance value. If the resistor element is subjected to stresses, the resistance path literally changes and so the value of the resistance changes. On the other hand, any trace of water or water vapor causes deleterious effects in resistors resulting in oxidation or electrolysis upon application of a small load or polarizing voltage. When the latter phenomenon occurs, the stability of the resistor is affected and there is a continued increase in resistance until the component eventually opens and a catastrophic failure takes place. Obviously the manufacturer and the user of electrical resistors would prefer to have electrical resistors which do not become affected by either stress or humidity.
There have been many attempts to protect resistors from the humidity, the U.S. Pat. No. 4,010,440 assigned to the assignee of this application being an example. However, such attempts have not included the feature to also protect the resistor from stresses. On the other hand there have been some attempts to protect the resistor package from mechanical forces, the U.S. Pat. No. 3,405,381 being an example. However, in the U.S. Pat. No. 3,405,381 the naked element is encapsulated in an epoxy or plastic coating as a moisture barrier before being encapsulated in a soft material, and hence the stresses which are generated by heat can cause distortions in the resistance value because of the difference in temperature coefficient of expansion between the epoxy coating, coming in contact with the naked substrate, and the substrate.